In the proposed studies, we plan to purify the intranuclear receptors for triiodothyronine (T3). Use will be made of affinity chromatography and photoaffinity labelling of the receptors. We also plan to characterize the factors (including histones) that appear to stimulate the receptor's ability to bind T3 with high affinity. Finally, we hope to determine the influence of the T3-receptor interaction on chromatin structure.